Method and System for Storing Query Plans in a Cache and Method for Querying a Database System

2. The method of claim 1, wherein the compression level of query plans includes an uncompressed level, a medium compression level, or a high compression level.

4. The method of claim 1, wherein the compression change includes compression or decompression of a portion of the at least one query operator.

5. The method of claim 1, wherein each of the at least one query operator further comprises a query expression, and the compression change further comprises compression or decompression of a portion of the query expression.

7. The method of claim 1, wherein the at least two storage layers includes a third storage layer and a second storage layer, the second storage layer is associated with higher compression level than the third storage layer, and query plans stored in the second storage layer are associated with lower use frequencies than query plans stored in the third storage layer.

8. The method of claim 1, wherein a counter is associated with the query plan, the counter counting a number of times the query plan is accessed to generate query results.

14. The method of claim 11, wherein the query plan is stored in the cache in association with a reference key.